Original Date: 11/03/1996
Revision Date: 01/18/2007

The Oak Ridge Y-12 Plant has developed the Vector Displacement Interferometer (VDI) which offers an alternative method for mapping positioning errors on coordinate measuring machines and machine tools. The VDI (Figure 3-4) provides a simpler and faster process than traditional laser trackers.

Conventional mapping techniques use an expensive and time-consuming process, and require the user to be trained in the operation of specialized equipment. The user must map the three translational and three rotational motion errors of each slide; measure the squareness errors between the slides; and then calculate the positioning error from the error components by using rigid body motion equations.

The VDI provides a different approach. The user measures all machine displacements directly with the VDI. By taking three sets of measurements from three separate observation points, the user can mathematically combine the values to calculate the x, y, and z positioning error components. Unlike conventional laser trackers, the VDI does not contain a laser. Instead, a fiber optic cable delivers the laser beam to the device. This feature reduces the device’s size and eliminates heat as an error source. In addition, the small size allows the user to place the device directly on the table of the machine being mapped.

From its relative ease and speed, the VDI mapping process provides additional benefits. Users can generate uncertainty estimates, use 3-D interpolation directly to compensate for positioning errors, eliminate rigid body motion assumptions, and produce slide parametric error estimates from the x, y, and z positioning error components in diagnostic situations.

The Oak Ridge Y-12 Plant currently runs qualification experiments with the VDI equipment. With its efficiency, portability, and versatility, the VDI will allow users to explore new applications.

For more information see the Point of Contact for this survey.